WO2021153730A1

WO2021153730A1 - Electrolytic capacitor and method for producing same

Info

Publication number: WO2021153730A1
Application number: PCT/JP2021/003234
Authority: WO
Inventors: 博之有馬; 丈博小林
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2020-01-31
Filing date: 2021-01-29
Publication date: 2021-08-05
Also published as: CN115039191A; US20230078283A1; JPWO2021153730A1

Abstract

Disclosed is an electrolytic capacitor (100) including a capacitor element (10). The capacitor element (10) includes: a positive electrode on the surface of which a dielectric layer is formed; and an electrolyte layer disposed adjoining the dielectric layer. The electrolyte layer includes: a conductive polymer that has been doped with a dopant; conductive particles; and a non-aqueous solvent.

Description

Electrolytic capacitors and their manufacturing methods

This disclosure relates to electrolytic capacitors and their manufacturing methods.

Capacitors used in electronic devices are required to have a large capacity and a low equivalent series resistance (ESR) value in the high frequency region. As a capacitor having a large capacity and a low ESR, an electrolytic capacitor using a conductive polymer such as polypyrrole, polythiophene, polyfuran, or polyaniline is promising. Patent Document 1 (International Publication No. 2012/11794) describes "a conductive polymer and a polysulfonic acid that functions as a dopant for the conductive polymer" as a conductive polymer solution for forming a solid electrolyte layer. Alternatively, a conductive polymer solution containing a salt thereof, a mixture of polyacid and a carbon material, and a solvent ”is disclosed (claim 1 of Patent Document 1). Further, Patent Document 1 discloses a solid electrolytic capacitor manufactured by using the conductive polymer solution.

International Publication No. 2012/119794

Currently, there is a demand for electrolytic capacitors with a low rate of increase in ESR over a long period of time. In such a situation, one of the objects of the present disclosure is to provide an electrolytic capacitor having a low rate of increase in ESR over a long period of time.

One aspect of this disclosure relates to electrolytic capacitors. The electrolytic capacitor is an electrolytic capacitor including a capacitor element, and the capacitor element includes an anode having a dielectric layer formed on its surface and an electrolyte layer arranged adjacent to the dielectric layer. The electrolyte layer contains a conductive polymer doped with a dopant, conductive particles, and a non-aqueous solvent.

Another aspect of this disclosure relates to a method of manufacturing an electrolytic capacitor. The manufacturing method includes a step (i) of preparing a capacitor element precursor containing an anode having a dielectric layer formed on its surface, and a polymer layer containing a dopant-doped conductive polymer and conductive particles. Is included in a step (ii) of forming the polymer layer adjacent to the dielectric layer by an impregnation treatment and a step (iii) of impregnating the polymer layer with a non-aqueous solvent.

According to the present disclosure, an electrolytic capacitor having a low rate of increase in ESR over a long period of time can be obtained.
Although the novel features of the present invention are described in the appended claims, the present invention is further described in the following detailed description with reference to the drawings, in combination with other objects and features of the present invention, both in terms of structure and content. It will be well understood.

It is sectional drawing which shows typically an example of the electrolytic capacitor of this disclosure. It is a figure which shows a part of the electrolytic capacitor shown in FIG. 1 schematically.

Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained.

(Electrolytic capacitor)
The electrolytic capacitor of the present disclosure includes a capacitor element. The capacitor element includes an anode having a dielectric layer formed on its surface and an electrolyte layer arranged adjacent to the dielectric layer. The electrolyte layer contains a dopant-doped conductive polymer, conductive particles, and a non-aqueous solvent.

The capacitor element is formed between a foil-shaped anode having a dielectric layer formed on its surface, a foil-shaped cathode body, a separator arranged between the anode body and the cathode body, and between the anode body and the cathode body. It may include an electrolyte layer arranged in. Such a capacitor element may be referred to as a "first capacitor element" below. The first capacitor element may be a winding type or a laminated type. In an example of the winding type capacitor element, the foil-shaped anode body, the foil-shaped cathode body, and the separator are wound so that the separator is arranged between the anode body and the cathode body. In an example of the laminated capacitor element, the foil-shaped anode body, the foil-shaped cathode body, and the separator are folded in a zigzag shape so that the separator is arranged between the anode body and the cathode body.

Alternatively, the capacitor element may include a porous anode body having a dielectric layer formed on its surface, a cathode layer, and an electrolyte layer arranged between the anode body and the cathode layer. Such a capacitor element may be referred to as a "second capacitor element" below. In the first and second capacitor elements, the electrolyte layer is adjacent to the dielectric layer formed on the surface of the anode.

(Conductive polymer)
The conductive polymer contained in the electrolyte layer will be described below.

Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. The derivatives include polymers based on polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene. For example, derivatives of polythiophene include poly (3,4-ethylenedioxythiophene) and the like. These conductive polymers may be used alone or in combination of two or more. Further, the conductive polymer may be a copolymer of two or more kinds of monomers. The weight average molecular weight of the conductive polymer is not particularly limited, and may be in the range of, for example, 1000 to 100,000. A preferred example of the conductive polymer is poly (3,4-ethylenedioxythiophene) (PEDOT).

Dopants are doped into the conductive polymer. From the viewpoint of suppressing dedoping from the conductive polymer, it is preferable to use a polymer dopant as the dopant. Examples of high molecular weight dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly (2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, Includes polyacrylic acid and the like. These may be used alone or in combination of two or more. Some of these may be included in the electrolyte layer in the form of salts. A preferred example of a dopant is polystyrene sulfonic acid (PSS).

The weight average molecular weight of the dopant is not particularly limited. From the viewpoint of facilitating the formation of a homogeneous electrolyte layer, the weight average molecular weight of the dopant may be in the range of 1000 to 100,000.

In the electrolytic capacitor of the present disclosure, the dopant may be polystyrene sulfonic acid, and the conductive polymer may be poly (3,4-ethylenedioxythiophene). That is, the electrolyte layer may contain polystyrene sulfonic acid-doped poly (3,4-ethylenedioxythiophene).

(Liquid component)
The electrolyte layer of the electrolytic capacitor of the present disclosure contains a non-aqueous solvent. The electrolyte layer may contain an electrolytic solution (non-aqueous electrolytic solution) containing a non-aqueous solvent and a basic component dissolved in the non-aqueous solvent. That is, the electrolyte layer of the electrolytic capacitor of the present disclosure may contain a liquid component. Hereinafter, the liquid component (non-aqueous solvent or electrolytic solution) contained in the electrolyte layer may be referred to as “liquid component (L)”. In this specification, the liquid component (L) may be a component that is liquid at room temperature (25 ° C.) or a component that is liquid at the temperature at which the electrolytic capacitor is used. .. An electrolytic capacitor having an electrolyte layer containing a liquid component (L) may be called a hybrid capacitor.

The non-aqueous solvent contained in the electrolyte layer may be an organic solvent or an ionic liquid. Examples of non-aqueous solvents include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), N-methylacetamide, N, N-. Includes amides such as dimethylformamide and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methylethylketone, and formaldehyde. ..

Alternatively, a polymer solvent may be used as the non-aqueous solvent. Examples of the polymer solvent include polyalkylene glycols, derivatives of polyalkylene glycols, compounds in which at least one hydroxyl group in a polyhydric alcohol is replaced with polyalkylene glycol (including a derivative), and the like. Specifically, examples of polymer-based solvents include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, and polypropylene glycol diglyceryl ether. Polyethylene glycol sorbitol ether, polybutylene glycol and the like are included. Examples of the polymer solvent further include a copolymer of ethylene glycol-propylene glycol, a copolymer of ethylene glycol-butylene glycol, a copolymer of propylene glycol-butylene glycol, and the like. As the non-aqueous solvent, one type may be used alone, or two or more types may be mixed and used.

As described above, the electrolyte layer may contain a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. Further, the electrolyte layer may contain a non-aqueous solvent and a base component and / or an acid component (acid) dissolved in the non-aqueous solvent.

As the acid component, polycarboxylic acid and monocarboxylic acid can be used. Examples of the above polycarboxylic acids include aliphatic polycarboxylic acids ([saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebatic acid, 1 , 6-decandicarboxylic acid, 5,6-decandicarboxylic acid]; [unsaturated polycarboxylic acid, eg maleic acid, fumaric acid, icotanic acid]), aromatic polycarboxylic acid (eg phthalic acid, isophthalic acid, terephthalic acid) , Trimellitic acid, pyromellitic acid), alicyclic polycarboxylic acid (for example, cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

Examples of the above monocarboxylic acids include aliphatic monocarboxylic acids (1 to 30 carbon atoms) ([saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, etc. Capricic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, bechenic acid]; [unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, oleic acid]) Acids, naphthoic acids), oxycarboxylic acids (eg salicylic acid, mandelic acid, resorcinic acid).

Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcinic acid are thermally stable and are preferably used.

Inorganic acid may be used as the acid component. Typical examples of inorganic acids are phosphoric acid, phosphite, hypophosphite, alkyl phosphate ester, boric acid, boric acid, boric acid tetrafluoride, phosphoric acid hexafluoride, benzenesulfonic acid, naphthalenesulfone. Examples include acid. Further, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such complex compounds include borodiglycolic acid, borodioxalic acid, borodisalicylic acid and the like.

The base component may be a compound having an alkyl-substituted amidine group, for example, an imidazole compound, a benzimidazole compound, an alicyclic amidine compound (pyrimidine compound, imidazoline compound) or the like. Specifically, 1,8-diazabicyclo [5,4,0] undecene-7, 1,5-diazabicyclo [4,3,0] nonen-5, 1,2-dimethylimidazolinium, 1,2, 4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptyl imidazoline, 1-methyl-2- (3'heptyl) imidazoline, 1- Methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole and 1-methylbenzoimidazole are preferred. By using these, a capacitor having excellent impedance performance can be obtained.

As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group may be used. Examples of such basic components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with alkyl or arylalkyl groups having 1 to 11 carbon atoms. Be done. Specifically, 1-methyl-1,8-diazabicyclo [5,4,0] undecene-7, 1-methyl-1,5-diazabicyclo [4,3,0] nonen-5,1,2,3 -Trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1, , 3-Dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2- (3'heptyl) imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl- 1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzoimidazolium are preferred. By using these, a capacitor having excellent impedance performance can be obtained.

Alternatively, a tertiary amine may be used as a base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyln-propylamine, methylethylisopropylamine, diethyl-n- Propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.) ). Among them, trialkylamines are preferable from the viewpoint of increasing the conductivity of the electrolyte layer, and it is more preferable to contain at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine and triethylamine. Further, as a base component, a secondary amine such as dialkylamines, a primary amine such as monoalkylamine, or ammonia may be used.

The liquid component (L) may contain a salt of an acid component and a base component. The salt may be an inorganic salt and / or an organic salt. An organic salt is a salt in which at least one of an anion and a cation contains an organic substance. Examples of the organic salt include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono1,2,3,4-tetramethylimidazolinium phthalate, and mono 1,3-dimethyl-2-phthalate. Ethylimidazolinium or the like may be used. Even when the liquid component (L) contains a salt of an acid component and a base component, dedoping is likely to occur due to the base component contained in the salt, so that the configuration of the present disclosure is particularly effective.

In order to suppress the dedoping of the dopant, the pH of the liquid component (L) may be less than 7, or 5 or less (for example, in the range of 2 to 4.5).

It is important that the ESR of electrolytic capacitors is low. A low ESR can be achieved by using an electrolyte layer containing a conductive polymer doped with a dopant. However, when an electrolyte layer containing a conductive polymer doped with a dopant and a liquid component (L) is used, the present inventors have stated that although the initial ESR is low, the deterioration phenomenon in which the ESR increases with time is large. Found. As a result of investigating the cause, it was found that the dopant may be easily dedoped in the electrolyte layer containing the liquid component (L). It is believed that this dedoping increases the ESR over time. Therefore, it is important to suppress an increase in ESR over time in an electrolytic capacitor containing a liquid component (L) as compared with a solid electrolytic capacitor containing a solid electrolyte containing no liquid component (L).

Since the conductive polymer has high conductivity, it is effective in reducing ESR. However, the conductivity of the conductive polymer decreases due to deterioration over time, so that the ESR increases. In particular, when the electrolyte layer contains the liquid component (L), the increase in ESR becomes large. On the other hand, it is considered that the conductivity of the conductive particles hardly deteriorates with time. Therefore, by adding the conductive particles, it is possible to suppress an increase in ESR with time.

In the electrolytic capacitor of the present disclosure, the dopant may be a dopant containing an acidic group or a polymer dopant containing an acidic group. As a result of examination, the inventors of the present application have newly found that when a dopant containing an acidic group is used, dedoping may occur remarkably as the pH increases. Therefore, when a dopant containing an acidic group is used, it is particularly important to suppress an increase in ESR over time.

In the electrolytic capacitor of the present disclosure, the dopant may be a polymer dopant containing an acidic group, and the electrolyte layer may contain an electrolytic solution containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent. good. In this case, since dedopant is likely to occur due to the base component, it is particularly important to suppress an increase in ESR over time. As described above, since the electrolytic capacitor of the present disclosure contains conductive particles, it is possible to suppress an increase in ESR over time.

Examples of acidic groups include sulfonic acid groups, carboxyl groups and the like. A polymer dopant containing an acidic group is a polymer in which at least a part of its constituent units contains an acidic group. Examples of such polymeric dopants include the polymeric dopants described above.

In the electrolytic capacitor of the present disclosure, the content of the base component in the electrolytic solution may be 0.1% by mass or more and 20% by mass or less. When the amount of the base component is 0.1% by mass or more, it is particularly important to use conductive particles. Further, by setting the amount of the base component to 20% by mass or less, it becomes easy to dissolve the base component in the electrolytic solution. When the electrolytic solution contains a salt of an acid component and a base component (for example, when the electrolytic solution contains the salt as a solute), the content of the base component in the electrolytic solution is the mass of the electrolytic solution and the salt. It is obtained from the mass of our base component.

The content of the liquid component (L) in the electrolyte layer may be in the range of 50 to 99.5% by mass. The total content of the conductive polymer and the dopant in the electrolyte layer may be in the range of 0.5 to 10% by mass. The content of the conductive particles in the electrolyte layer may be in the range of 0.025 to 5% by mass. The total mass Wm (g) of the conductive polymer and the dopant contained in the electrolyte layer and the mass Wp (g) of the conductive particles contained in the electrolyte layer may satisfy 1 <Wm / Wp, for example. 2 ≦ Wm / Wp ≦ 20 may be satisfied. Alternatively, the ratio Wp / Wm may be 0.05 or more, 0.15 or more, 0.35 or more, 0.50 or more, or 1.0 or more. The ratio Wp / Wm may be 10 or less, 5.0 or less, or 2.0 or less. These lower and upper limits can be combined arbitrarily. For example, the ratio Wp / Wm may be in the range of 0.05 to 10, 0.15 to 10, 0.35 to 10, 0.50 to 10, or 1.0 to 10. good. The upper limit of any of these ranges may be replaced with 5.0 or 2.0. By setting the ratio Wp / Wm to 0.05 or more (for example, 0.15 or more, 0.35 or more, or 1.0 or more), an electrolytic capacitor having a particularly low ESR increase rate can be obtained. By setting the ratio Wp / Wm to 10 or less (for example, 5.0 or less or 2.0 or less), ESR can be particularly reduced, and a decrease in capacitance can also be suppressed. The ratio Wp / Wm is equal to (content of conductive particles in the electrolyte layer) / (total content of conductive polymer and dopant in the electrolyte layer).

(Conductive particles)
The conductive particles contained in the electrolyte layer will be described below. The conductive particles are particles made of a conductive material. The conductive particles are different from the above-mentioned conductive polymer. The conductive particles are typically made of a non-polymeric material.

The conductive particles contained in the electrolyte layer may be only one type of conductive particles, or may contain a plurality of types of conductive particles. The conductive particles may be particles of a conductive carbon material or particles made of a material other than the conductive carbon material. Examples of materials other than conductive carbon materials include conductive nickel-phosphorus (Ni-P) materials, conductive indium-tin (In-Sn) materials, conductive tin oxide, and conductive tin-silver. (Sn-Ag) and the like are included. The conductive particles may be metal particles (for example, nickel or other metal particles).

In the electrolytic capacitor of the present disclosure, the conductive particles may include at least one particle selected from the group consisting of carbon black particles, carbon nanotube particles, graphite particles, and graphene particles. These particles are preferable because the average particle size, the structure of the particles, and the surface texture can be controlled in various ways. The conductive particles may be composed of only one kind of particles among these particles, or may be composed of a plurality of kinds of particles among these particles.

In the electrolytic capacitor of the present disclosure, the total mass of the conductive polymer and the dopant contained in the electrolyte layer may be larger than the mass of the conductive particles contained in the electrolyte layer. That is, the total content (mass%) of the conductive polymer and the dopant in the electrolyte layer may be larger than the content (mass%) of the conductive particles in the electrolyte layer. The above-mentioned conductive polymer is generally more conductive than the above-mentioned conductive particles. Therefore, increasing the content of the conductive polymer is effective in reducing the initial ESR.

The electrolytic capacitor of the present disclosure may satisfy the following conditions (1) and (2).
(1) The anode has a porous portion on the surface (the surface on which the dielectric layer is formed), and the average particle size of the conductive particles is larger than the average pore diameter of the porous portion on the surface of the anode. big.
(2) The conductive polymer is in the form of particles, and the average particle size of the conductive polymer is smaller than the average pore size of the porous portion on the surface of the anode.

As described above, the above-mentioned conductive polymer is generally more conductive than the above-mentioned conductive particles. Therefore, it is possible to lower the initial ESR by arranging the conductive polymer near the surface of the anode. When the above conditions (1) and (2) are satisfied, the conductive polymer is likely to be arranged in the voids (pores) of the porous portion of the anode body. That is, the conductive polymer is easily arranged in the portion of the surface of the anode body close to the dielectric layer. As a result, the initial ESR can be lowered.

In this specification, the average particle size of the particles is the median diameter (D ₅₀ ) at which the cumulative volume is 50% in the volume-based particle size distribution. The median diameter is determined using, for example, a laser diffraction / scattering particle size distribution measuring device.

In this specification, the average pore diameter of the porous portion on the surface of the anode is the median diameter (D ₅₀ ) at which the cumulative volume is 50% in the volume-based pore distribution. The median diameter is determined using, for example, gas adsorption pore distribution measurement.

The electrolytic capacitor of the present disclosure may satisfy the following condition (3).
(3) The electrolyte layer includes a polymer layer (conductive polymer layer) composed of a conductive polymer, and the polymer layer is the first polymer layer formed on the dielectric layer on the surface of the anode. It includes a polymer layer and a second polymer layer formed on the first polymer layer. That is, the first polymer layer is arranged between the dielectric layer on the surface of the anode and the second polymer layer.

When the electrolyte layer contains the first and second polymer layers, the conductive polymer contained in the first polymer layer and the conductive polymer contained in the second polymer layer are the same. It may or may not be different. The conductive particles may be contained in both the first and second polymer layers, or may be contained in only one of them. When both the first and second polymer layers contain conductive particles, the conductive particles contained in the first polymer layer and the conductive particles contained in the second polymer layer are the same. It may or may not be different.

The electrolytic capacitor of the present disclosure may satisfy the above conditions (3) and the following conditions (4).
(4) The content rate (mass%) of the conductive particles in the second polymer layer is larger than the content rate (mass%) of the conductive particles in the first polymer layer. The conductive particles may be contained in both the first and second polymer layers, or may be contained only in the second polymer layer.

The condition of (4) above is that (4') the content of the conductive polymer in the first polymer layer (mass%) is the content of the conductive polymer in the second polymer layer (mass). It may be replaced with the condition that it is larger than%). By lowering the content of the conductive particles in the first polymer layer and increasing the content of the conductive polymer, the proportion of the conductive polymer in the portion of the surface of the anode near the dielectric layer Can be raised. As a result, the initial ESR can be lowered.

The electrolytic capacitor of the present disclosure may satisfy the following conditions (A) and (B), and may further satisfy the condition (C). By satisfying these conditions, an electrolytic capacitor having high characteristics and reliability can be obtained.
(A) The conductive polymer is poly (3,4-ethylenedioxythiophene), and the dopant is polystyrene sulfonic acid.
(B) The conductive particles are particles of a conductive carbon material, for example, at least one particle selected from the group consisting of carbon black particles, carbon nanotube particles, graphite particles, and graphene particles. Alternatively, the conductive particles may be at least one selected from the group consisting of metal particles and particles of a conductive carbon material.
(C) The total mass Wm (g) of the conductive polymer and the dopant contained in the electrolyte layer and the mass Wp (g) of the conductive particles contained in the electrolyte layer satisfy 1 <Wm / Wp, for example. , 2 ≦ Wm / Wp ≦ 20 is satisfied. Alternatively, the ratio Wp / Wm may be in the above range.

The components (anode body, cathode body, separator, etc.) of the capacitor element other than the electrolyte are not particularly limited, and known ones may be used. Examples of those of the first capacitor element will be described below.

(Anode)
As the anode body, a metal foil having a dielectric layer formed on its surface may be used. The type of metal constituting the metal foil is not particularly limited. Examples of metals constituting the metal foil include valve-acting metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve-acting metals because of the ease of formation of the dielectric layer. .. A preferred example is aluminum and aluminum alloys. Normally, the surface of the anode is roughened (porous). The dielectric layer of the anode body is formed on a porous portion (roughened surface). The electrolyte layer is in contact with the dielectric layer of the anode.

(Cathode)
A metal foil may be used for the cathode body. The type of metal constituting the metal foil is not particularly limited. Examples of the metals that make up the metal leaf include valvular metals such as aluminum, tantalum, niobium, titanium, and alloys of valvular metals. A preferred example is aluminum and aluminum alloys. A chemical conversion film may be provided on the surface of the cathode body, or a metal (dissimilar metal) or non-metal film different from the metal constituting the cathode body may be provided. Examples of dissimilar metals and non-metals include metals such as titanium and non-metals such as carbon.

(Separator)
As the separator, a sheet-like material that can be impregnated with an electrolyte can be used. For example, a sheet-like material that has insulating properties and can be impregnated with an electrolyte may be used. The separator may be a woven fabric, a non-woven fabric, or a porous membrane. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

Examples of components other than the electrolyte layer of the second capacitor element will be described below. The second capacitor element includes a porous anode body having a dielectric layer formed on its surface, a cathode layer, and an electrolyte layer arranged between the anode body and the cathode layer.

The porous anode body may be, for example, a porous sintered body obtained by sintering material particles containing a valve acting metal. The anode body may have a rectangular parallelepiped shape. Examples of valve acting metals include titanium (Ti), tantalum (Ta), niobium (Nb) and the like. The material particles may be made of an alloy containing a valve acting metal. For example, an alloy containing a valve acting metal and silicon, vanadium, boron or the like may be used. The valve-acting metal alloy contains the valve-acting metal as a main component, and for example, contains 50 atomic% or more of the valve-acting metal. Further, material particles composed of a compound containing a valve acting metal and a typical element such as nitrogen may be used. As the material particles, one type may be used alone, or two or more types may be mixed and used.

Since the anode of the second capacitor element is porous, it has a porous portion on the surface, and the dielectric layer is formed in the porous portion. The electrolyte layer is in contact with the dielectric layer of the anode. The dielectric layer is formed, for example, by subjecting a sintered body to be an anode body to a chemical conversion treatment and growing an oxide film on the surface of the sintered body.

The cathode layer has a current collecting function. The cathode layer is formed of, for example, a conductive material. The cathode layer may be a conductive layer formed so as to cover the electrolyte layer. The cathode layer may include a carbon layer formed so as to cover the electrolyte layer and a metal paste layer formed on the carbon layer. The carbon layer may contain a conductive carbon material such as graphite and a resin. The metal paste layer may contain metal particles (for example, silver particles) and a resin. The cathode layer can be formed by applying the above material or the like.

(Manufacturing method of electrolytic capacitor)
The method of the present disclosure for manufacturing an electrolytic capacitor will be described below. According to this manufacturing method, the electrolytic capacitor of the present disclosure can be manufactured. Since the matters described about the electrolytic capacitor of the present disclosure can be applied to the following manufacturing methods, duplicate description may be omitted. For example, since the components of the capacitor element and the like have been described above, duplicate description may be omitted. In addition, the matters described in the following manufacturing method can be applied to the above-mentioned electrolytic capacitor.

The manufacturing method according to the present disclosure includes step (i), step (ii), and step (iii). They will be described below.

(Step (i))
Step (i) is a step (i) of preparing a capacitor element precursor containing an anode having a dielectric layer formed on its surface. The step (i) may be a step of forming a capacitor element precursor by a known method.

When manufacturing an electrolytic capacitor including the first capacitor element, the step (i) involves a foil-shaped anode having a dielectric layer formed on its surface, a foil-shaped cathode body, and an anode body and a cathode body. It may be a step of forming a capacitor element precursor including a separator arranged between them. In this case, as described above, the capacitor element precursor may be a wound type or a laminated type. When manufacturing an electrolytic capacitor including a second capacitor element, the capacitor element precursor is an anode having a dielectric layer formed on its surface (a porous anode) and a part thereof embedded in the anode. It may be composed of an anode wire.

(Process (ii))
Step (ii) is a step of forming a polymer layer containing a conductive polymer doped with a dopant and conductive particles so as to be adjacent to the dielectric layer by an impregnation treatment.

The impregnation treatment in step (ii) may be an impregnation treatment (x) in which the capacitor element precursor is impregnated with a dispersion liquid containing a conductive polymer doped with a dopant and conductive particles. For example, the dispersion liquid can be impregnated by immersing the capacitor element precursor in the dispersion liquid. By removing (drying) the dispersion medium of the dispersion liquid impregnated in the capacitor element precursor, the polymer layer containing the dopant-doped conductive polymer and the conductive particles is adjacent to the dielectric layer. Can be placed in. The impregnation treatment (x) may be performed a plurality of times. In that case, a drying step of removing the dispersion medium of the impregnated dispersion may be performed before the second and subsequent impregnation treatments (x) are performed.

The dispersion medium of the dispersion is not particularly limited, and a known dispersion medium may be used. For example, as the dispersion medium, an aqueous liquid containing water may be used, or water may be used.

The content of the conductive polymer and the conductive particles in the dispersion is not particularly limited, and may be any content that can be impregnated. The content of the conductive polymer in the dispersion may be in the range of, for example, 0.1% by mass to 10% by mass. The content of the conductive particles in the dispersion may be adjusted according to the content of the conductive polymer.

By adjusting the mass (content rate) of the conductive polymer and the mass (content rate) of the conductive particles in the dispersion liquid, the ratio thereof in the formed electrolyte layer can be adjusted. For example, by making the mass (content rate) of the conductive polymer in the dispersion liquid larger than the mass (content rate) of the conductive particles in the dispersion liquid, the mass of the conductive polymer contained in the electrolyte layer can be increased. , It can be larger than the mass of the conductive particles contained in the electrolyte layer.

The impregnation treatment in the step (ii) may include an impregnation treatment (y) and an impregnation treatment (z). In the impregnation treatment (y) and the impregnation treatment (z), the impregnation treatment (y) may be performed first, the impregnation treatment (z) may be performed first, or the impregnation treatment (z) may be performed at the same time. In a preferred example, the impregnation treatment (y) is followed by the impregnation treatment (z). The impregnation treatment (y) and the impregnation treatment (z) may be independently performed a plurality of times. Further, after each of the impregnation treatment (y) and the impregnation treatment (z), a drying step of removing the dispersion medium of the impregnated dispersion may be performed.

The impregnation treatment (y) is an impregnation treatment in which the capacitor element precursor is impregnated with a first dispersion liquid containing a conductive polymer doped with a dopant. The impregnation treatment (z) is an impregnation treatment for impregnating the capacitor element precursor with a second dispersion liquid containing conductive particles. As for the dispersion medium and the impregnation method of the first and second dispersion liquids, the dispersion medium and the impregnation method described in the impregnation treatment (x) may be applied.

In one example, the first dispersion does not contain conductive particles and the second dispersion does not contain a dopant-doped conductive polymer. However, the first dispersion may contain conductive particles and the second dispersion may contain a dopant-doped conductive polymer.

The case where both the first and second dispersion liquids contain a conductive polymer doped with a dopant will be described. In this case, one of the impregnation treatment (y) and the impregnation treatment (z) may be performed, followed by drying, and then the other impregnation treatment. By doing so, a polymer layer including the first polymer layer and the second polymer layer can be formed. Further, by adjusting the content of the conductive particles in the first dispersion liquid and the content of the conductive particles in the second dispersion liquid, the content of the conductive particles in the first polymer layer and the first The content of conductive particles in the polymer layer of 2 can be adjusted.

(Step (iii))
Step (iii) is a step of impregnating the polymer layer formed in step (ii) with a non-aqueous solvent. As a result, an electrolyte layer containing a conductive polymer doped with a dopant, conductive particles, and a non-aqueous solvent is formed. The step (iii) may be a step of impregnating the polymer layer formed in the step (ii) with an electrolytic solution containing a non-aqueous solvent. That is, the step (iii) may be a step of impregnating the polymer layer formed in the step (ii) with the liquid component (L).

The impregnation method in step (iii) is not particularly limited, and a known method may be used. For example, the capacitor element precursor that has undergone step (ii) may be immersed in a non-aqueous solvent (or electrolytic solution). The above-mentioned ones can be applied to the non-aqueous solvent (or electrolytic solution) used in the step (iii).

In the production method of the present disclosure, the dopant may be a polymer dopant containing an acidic group, and in step (iii), an electrolytic solution containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent is polymerized. It may be a step of impregnating the layer.

The first capacitor element is obtained by the step (iii). Alternatively, step (iii) provides the anode and electrolyte layer of the second capacitor element. After the step (iii), an electrolytic capacitor may be manufactured using the components obtained in the step (iii). The process is not particularly limited, and a known method can be used.

Hereinafter, an example of the electrolytic capacitor according to the present disclosure will be specifically described with reference to the drawings, but the electrolytic capacitor of the present disclosure is not limited by the following figures. The above-mentioned components can be applied to the components of the electrolytic capacitor of the example described below. Further, the components of the electrolytic capacitor of the example described below can be changed based on the above description. In addition, the matters described below may be applied to the above-described embodiment. The same parts may be designated by the same reference numerals and duplicate description may be omitted.

(Embodiment 1)
In the first embodiment, an example of the electrolytic capacitor according to the present disclosure will be described. This electrolytic capacitor is an electrolytic capacitor including a first capacitor element. FIG. 1 schematically shows a cross section of an example of the electrolytic capacitor 100 of the first embodiment. FIG. 2 shows a schematic view of a part of the capacitor element 10 included in the electrolytic capacitor 100 shown in FIG.

As shown in FIG. 1, the electrolytic capacitor 100 includes a capacitor element 10, a bottomed case 11 that houses the capacitor element 10, a sealing member 12 that closes the opening of the bottomed case 11, and a seat that covers the sealing member 12. It includes a plate 13,

lead wires

14A and 14B derived from the sealing member 12 and penetrating the seat plate 13, and lead

tabs

15A and 15B connecting the

lead wires

14A and 14B and the electrodes of the capacitor element 10. The capacitor element 10 is housed in the bottomed case 11. The vicinity of the open end of the bottomed case 11 is drawn inward, and the open end of the bottomed case 11 is curled so as to crimp the sealing member 12.

With reference to FIG. 2, the capacitor element 10 includes a foil-shaped anode body 21 having a dielectric layer formed on its surface, a foil-shaped cathode body 22, and a separator 23 and an electrolyte layer arranged between them. (Not shown) and. The anode body 21 and the cathode body 22 are wound with the separator 23 arranged between them. The outermost circumference of the winding body is fixed by the winding stop tape 24. A lead tab 15A is connected to the anode body 21, and a lead tab 15B is connected to the cathode body 22. Note that FIG. 2 shows a partially unfolded state before fixing the outermost circumference of the wound body.

Hereinafter, embodiments of the present disclosure will be described in more detail by way of examples.

(Example)
[Manufacturing of capacitor A1]
The capacitor A1 is a winding type electrolytic capacitor having a rated voltage of 35 V and a rated capacitance of 270 μF. The capacitor A1 was manufactured by the following procedure.

(Preparation of cathode and anode)
As the cathode body, an Al foil (aluminum foil) having a thickness of 70 μm was used. An anode body having a dielectric layer formed on its surface was produced by the following procedure. First, an Al foil having a thickness of 120 μm was prepared. The Al foil was subjected to a direct current etching treatment to roughen the surface. Next, the Al foil was subjected to chemical conversion treatment. Specifically, the Al foil is immersed in an aqueous solution of ammonium adipate, and a dielectric layer (thickness) is formed on the surface of the Al foil by performing a chemical conversion treatment at 70 ° C. for 30 minutes while applying a voltage of 50 V to the Al foil. : About 70 nm) was formed. In this way, an anode body having a dielectric layer formed on its surface was obtained. Then, the anode body of the capacitor A1 was prepared by cutting the anode body to a predetermined size.

(PEDOT: Preparation of PSS dispersion)
A dispersion of a second conductive polymer doped with a dopant was prepared by the following method. First, a mixed solution of 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (dopant) was prepared by dissolving them in ion-exchanged water. While stirring the obtained mixed solution, iron (III) sulfate (oxidizing agent) dissolved in ion-exchanged water was added to carry out a polymerization reaction. After the reaction, the obtained reaction solution was dialyzed to remove unreacted monomers and excess oxidizing agent. In this way, a dispersion containing poly (3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (about 5% by mass with respect to poly (3,4-ethylenedioxythiophene)) was obtained. .. In the following, polystyrene sulfonic acid-doped poly (3,4-ethylenedioxythiophene) may be referred to as "PEDOT: PSS".

(PEDOT: Addition of conductive particles to PSS dispersion)
Nickel metal particles (spherical, average particle size: 2 μm) were added to the PEDOT: PSS dispersion. In this way, a treatment liquid A containing PEDOT: PSS and conductive particles was prepared.

(Making a wound body)
An anode lead tab and a cathode lead tab to which a lead wire was connected were connected to the anode body and the cathode body, respectively. Then, the anode body and the cathode body were wound with a separator in between, and the outer surface was fixed with a winding stopper tape. A non-woven fabric made of cellulose was used as the separator. In this way, a wound body (capacitor element precursor) was produced. The prepared wound body was immersed in an ammonium adipate solution, and chemical conversion treatment was performed again at 70 ° C. for 60 minutes while applying a voltage of 50 V to the anode body. By this chemical conversion treatment, a dielectric layer was formed mainly on the end face of the anode body.

(Formation of conductive polymer layer)
First, the treatment liquid A was placed in a container. Next, the winding body was immersed in the treatment liquid A in the container for 15 minutes in a reduced pressure atmosphere (40 kPa) at room temperature, and then the winding body was pulled up from the treatment liquid A. In this way, the wound body was impregnated with the treatment liquid A. Next, in the drying oven, the wound body was dried at 60 ° C. for 30 minutes, followed by drying at 150 ° C. for 30 minutes. As a result, the solvent contained in the treatment liquid A was dried. In this way, a conductive polymer layer containing conductive particles was formed.

(Immersion of electrolytic solution)
The wound body on which the conductive polymer layer was formed was impregnated with the electrolytic solution at room temperature under atmospheric pressure. As the electrolytic solution, polyethylene glycol, γ-butyrolactone, sulfolane, and mono (ethyldimethylamine) phthalate (solute) were used, and polyethylene glycol: γ-butyrolactone: sulfolane: mono (ethyldimethylamine) phthalate = 30:30 :. A solution mixed at a mass ratio of 20:20 was used. In this way, a capacitor element including an electrolyte layer was obtained. This capacitor element was sealed to complete an electrolytic capacitor. Then, while applying the rated voltage, the aging treatment was carried out at 130 ° C. for 2 hours. In this way, the capacitor A1 was obtained.

[Manufacturing of capacitors A2 and 3]
The capacitors A2 and A3 were manufactured under the same materials and conditions as the capacitors A1 except that the content of the conductive particles in the treatment liquid A was different.

[Manufacturing of capacitors B1 to B3]
The capacitors B1 to B3 were manufactured under the same materials and conditions as the capacitors A1 except that the types and contents of the conductive particles contained in the treatment liquid A were different. In the production of the capacitors B1 to B3, graphene (scaly, average particle size 0.4 μm) was used as the conductive particles.

[Manufacturing of capacitor C1 (comparative example)]
The capacitor C1 was manufactured under the same materials and conditions as the capacitor A1 except that conductive particles were not used. Therefore, the conductive polymer layer of the capacitor C1 contains PEDOT: PSS, but does not contain conductive particles.

(Measurement of ESR)
Equivalent series resistance (ESR) was measured for the electrolytic capacitors manufactured as described above. The ESR was measured using an LCR meter for 4-terminal measurement in an environment of 20 ° C. The ESR was measured by measuring the initial value after manufacturing the electrolytic capacitor and the value after leaving the electrolytic capacitor at a high temperature (leaving at 145 ° C. for 150 hours and 500 hours). Then, as an index of long-term characteristics, the ESR change rate was calculated by the following formula.
ESR change rate (%) = {100 x (ESR value after leaving at high temperature) / (initial ESR value)} -100

Table 1 shows some of the conditions for forming the electrolyte layer of the above electrolytic capacitor. The mass ratio (or content ratio) of the conductive particles and PEDOT: PSS in the formed electrolyte layer can be regarded as equal to the ratio of their content in the treatment liquid. Therefore, their mass ratios in the electrolyte layer were calculated from their content in the treatment solution. Table 2 shows the evaluation results of the ESR of the above electrolytic capacitor.

It is preferable that the ESR change rate is low. As shown in Table 2, in the electrolytic capacitor C1 of the comparative example, the ESR was significantly increased by leaving it at a high temperature. On the other hand, the ESR change rates of the electrolytic capacitors A1 to A3 and B1 to B3 were sufficiently low. The mass ratio of conductive particles / (PEDOT: PSS) was preferably 0.15 or more, more preferably 0.35 or more or 1.0 or more.

The present disclosure can be used for electrolytic capacitors and methods for manufacturing them.
Although the present invention has described preferred embodiments at this time, such disclosures should not be construed in a limited way. Various modifications and modifications will undoubtedly become apparent to those skilled in the art belonging to the present invention by reading the above disclosure. Therefore, the appended claims should be construed to include all modifications and modifications without departing from the true spirit and scope of the invention.

10 Capacitor element 21 Anode 22 Cathode 23 Separator 100 Electrolytic capacitor

Claims

An electrolytic capacitor that includes a capacitor element
The capacitor element includes an anode having a dielectric layer formed on its surface and an electrolyte layer arranged adjacent to the dielectric layer.
The electrolyte layer is an electrolytic capacitor containing a conductive polymer doped with a dopant, conductive particles, and a non-aqueous solvent.
The dopant is a polymer dopant containing an acidic group and
The electrolytic capacitor according to claim 1, wherein the electrolyte layer contains an electrolytic solution containing the non-aqueous solvent and a base component dissolved in the non-aqueous solvent.
The electrolytic capacitor according to claim 2, wherein the content of the base component in the electrolytic solution is 0.1% by mass or more and 20% by mass or less.
The electrolysis according to any one of claims 1 to 3, wherein the total mass of the conductive polymer and the dopant contained in the electrolyte layer is larger than the mass of the conductive particles contained in the electrolyte layer. Capacitor.
The electrolytic capacitor according to any one of claims 1 to 4, wherein the conductive particles are particles of a conductive carbon material.
The invention according to any one of claims 1 to 4, wherein the conductive particles include at least one particle selected from the group consisting of carbon black particles, carbon nanotube particles, graphite particles, and graphene particles. Electrolytic capacitor.
The anode has a porous portion on the surface and
The average particle size of the conductive particles is larger than the average pore size of the porous portion.
The conductive polymer is in the form of particles and is in the form of particles.
The electrolytic capacitor according to any one of claims 1 to 6, wherein the average particle size of the conductive polymer is smaller than the average pore size of the porous portion.
The electrolyte layer includes a polymer layer composed of the conductive polymer.
The polymer layer includes a first polymer layer formed on the dielectric layer and a second polymer layer formed on the first polymer layer.
The content of the conductive particles in the second polymer layer (mass%) is larger than the content of the conductive particles in the first polymer layer (mass%), according to claims 1 to 7. The electrolytic capacitor according to any one item.
The dopant is polystyrene sulfonic acid
The electrolytic capacitor according to any one of claims 1 to 8, wherein the conductive polymer is poly (3,4-ethylenedioxythiophene).
It is a manufacturing method of electrolytic capacitors.
The step (i) of preparing a capacitor element precursor containing an anode having a dielectric layer formed on its surface, and
A step (ii) of forming a polymer layer containing a dopant-doped conductive polymer and conductive particles so as to be adjacent to the dielectric layer by impregnation treatment.
A method for manufacturing an electrolytic capacitor, which comprises the step (iii) of impregnating the polymer layer with a non-aqueous solvent.
The dopant is a polymer dopant containing an acidic group and
The production method according to claim 10, wherein step (iii) is a step of impregnating the polymer layer with an electrolytic solution containing the non-aqueous solvent and a base component dissolved in the non-aqueous solvent.
The impregnation treatment in the step (ii) is an impregnation treatment (x) in which the capacitor element precursor is impregnated with a dispersion liquid containing the conductive polymer doped with the dopant and the conductive particles. Item 8. The production method according to Item 10.
The impregnation treatment in the step (ii) is
The impregnation treatment (y) of impregnating the capacitor element precursor with a first dispersion liquid containing the conductive polymer doped with the dopant.
The production method according to claim 10 or 11, further comprising an impregnation treatment (z) of impregnating the capacitor element precursor with a second dispersion liquid containing the conductive particles.
The dopant is polystyrene sulfonic acid
The production method according to any one of claims 10 to 13, wherein the conductive polymer is poly (3,4-ethylenedioxythiophene).